Apparatus for controlling the operation of circular knitting machines



Sept. 22, 1970 P. BROSE 3,529,445

APPARATUS FOR CONTROLLING THE OPERATION OF" CIRCULAR KNITTING MACHINES Filed April 1, 1969 4 Sheets-Sheet 1 Fig. 1

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APPARATUS FOR CONTROLLING THE OPERATION OF CIRCULAR KNITTING MACHINES Filed April 1, 1969 4 Sheets-Sheet L WWA A A A; A; WA A M A Fig. 5

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BY V PM Fwd? United States Patent O 3,529,445 APPARATUS FOR CONTROLLING THE OPERATION OF CIRCULAR KNITTING MACHINES Peter Brose, Wolfratshausen, Germany, assignor to Erwin Sick, Icking, Isartal, Germany Filed Apr. 1, 1969, Ser. No. 812,136 Claims priority, application Austria, Apr. 8, 1968,

' A 3,385/ 68 Int. Cl. D04b 35/10 US. Cl. 66-157 6 Claims ABSTRACT OF THE DISCLOSURE A control apparatus for a circular knitting machine including a photoelectric device for directing a light beam upon the knitting needles passing thereby, the light beam being reflected by the needles back upon a photoelectric receiver producing electrical signals solely as a result of the reflections which normally occur in a predetermined time sequence when the machine is in proper operating condition. When the electrical signals very from said predetermined time sequence due to the needles being damaged or missing, an integrating electrical network produces a perceptible indication that the yarn is not being properly knit by the machine.

The invention relates to apparatus for controlling the operation of circular knitting machines and in which a photoelectric sensing facility detects reflections from needles passing by the facility, the sensing facility out putting to evaluating means operated by irregularities of an ac. signal input to such means.

Apparatus of this kind has been disclosed in an article entitled Photoelektrische Warenkontrolle an Dopplezylinder-Automaten by Christian Schwabe, which appeared in Wirkereiund Strickerei-technik, 1964, 478- 482. In this apparatus an illuminating optical system forms a small light spot on a field of view through which the needles pass with the yarn on them. The field of view is imaged on a photoelectric receiver, for instance, by a light source being imaged on the field of view by way of a half-silvered mirror which is inclined to the optical axis of the illuminating optical system, while the field of view is imaged by the same optical system on a photoelectric receiver disposed behind such mirror.

The basis for the apparatus described is that in the event of needles being damaged or missing, there is a change in the position of the yarn relatively to the particular needle concerned, and this change becomes perceptible as an irregularity of the resulting a.c. signal, which can be used to indicate a fault and, if required, to stop the machine. In the prior arrangement there are difficulties in the way of satisfactorily evaluating the signal along the lines just mentioned. The signal arising from the yarn-containing field of view has a pattern which, although periodic, is fairly irregular during a single period; also, various other factors, such as thickness of the particular yarn used, cause irregularities. It must therefore be ascertained whether signal irregularity during a particular period allotted to the faulty needle deviates from the normal pattern as the later is given by sensing of the other needles. This normal pattern is relatively irregular within a single period but should be the same for all periods. Signal evaluation of this kind is feasible but requires a fairly large outlay.

It is an object of the invention to provide, using a relatively reduced outlay, a photoelectric system providing direct supervision of the needles of circular knitting machines.

In the apparatus according to the invention, the evaluat- ICC ing means are responsive to the time interval between the consecutive signals delivered by the sensing facility on the basis solely of reflections from the needles.

In other words, in contrast to the earlier disclosed arrangement yarn position on the needle is not observed and used as a criterion of whether the needle is faulty or not. Instead, the criterion for satisfactory operation of the machine is the sequence in time of the signals initiated purely by the reflections from the needles. If the needles are intact, such signals should follow one other at a particular known time interval. If any needle is bent, one of the pulses arrives either earlier or later, and so the time interval betwen the latter signal and the signals on either sideof it is shortened for one such adjacent needle and increased for the other. If a needle is missing, the time interval between two consecutive signals is twice the normal value. Needle supervision can therefore be based on a time measurement. There are a wide variety of ways of doing this. For instance, the signals produced by the re fiections from the needles could be compared with a sequence of set-value signals, so that an error signal is triggered off whenever the needle reflection signal varies from the set-value signal.

Very advantageously, the evaluating means comprise an integrating network receiving a constant input signal and resettable by the pulses delivered by the sensing facility; and a tripper is provided and responds when the output of the integration network exceeds a desired threshold. The integration member could be, for instance, a preselector counter whose input signal is a constant pulse frequency and which has been preselected to the desired threshold. The signals output by the sensing facility would zero-reset the counter.

In one very simple form of evaluating means, the integration network comprises a capacitor which is charged by a constant current and which upon the appearance of a signal from the sensing facility, is discharged so that sawtooth signals are produced; and the tripper has a threshold value which is the same as, or slightly larger than, sawtooth signal amplitude at the normal needle interval.

An embodiment of the invention will be described hereinafter with reference to the accompanying drawings wherein:

FIG. 1 is a perspective and diagrammatic view of part of a conventional circular knitting machine having photoelectric needle sensers according to the invention; FIG. 2 shows the beam path of a needle senser according to the invention;

FIG. 3 is a block schematic diagram of the associated evaluating circuitry;

FIG. 4 shows details of the circuitry shown in FIG. 3, and

FIG. 5 shows various signal patterns to explain the operation of the invention.

FIG. 1 is a diagrammatic view of a cylindrical needle cylinder 30 such as is used in a large circular knitting machine. Rib needles 32 and cylinder needles 31 are disposed on cylinder 30, which rotates during knitting. The needles 32 are at right-angles to the needles 31. The needles take up different positions during knitting.

The operation of such circular knitting machines is familiar and does not form part of this invention and so need not be described in detail here.

The needles always have the same positions at the places 35, 36 in FIG. 1. At such places, according to the invention a needle senser 34 senses the rib needles 32 and a needle senser 33 senses the cylinder needles 31, such sensing being photoelectric and of a kind which will be described hereinafter.

FIG. 2 shows the beam path of one such needle senser. A filament coil 1 of a lamp is imaged on a knitting needle 4 by a lens comprising lens elements 2, 3. The image is bounced back from the needle 4 to a photoelement 6 through the lens elements 3, 2 and through another lens element 5 which is disposed in the central part of the lens element 2. The photoelement 6 is mounted in an acrylic glass holder 7. A diaphragm 8 converts the beam of light from the lamp 1 into an annular b am; consequently, the light reaching the needle 4 is in the form of an annular beam passing via the outer portions of the lens element 2, 3, whereas the image is bounced back from the needle 4 via the central portions of the lens elements 2, 3, 5.

Two such sensing facilities are provided for large circular knitting machines using two needle rowsi.e., rib needles and cylinder needles. One facility supervises the rib needles and the other supervises the cylinder needles. Referring to FIG. 3, there can be seen the two photoelements 6, 6' of the two sensing facilities. One constant-current supply 9, 9 each charges up a respective capacitor 10, 10. The voltage across the capacitor therefore increases linearly. When the photoelements 6 detect a needle 4 and deliver a signal, the same is applied via an amplifier, and with opposite polarity to the capacitor charge, to the associated capacitor to discharge the same. Consequently, sawtooth signals such as the signals 19 in FIG. 5 are produced across the capacitors.

FIG. 5 shows the signals 17 delivered by the photoelements 6 and, in staggered relationship thereto, signals 18 delivered by the photo-elements 6. The signals 17 cooperate with the integration network 9, 10 to produce sawtooth signals which are staggered relatively to, but have the same amplitude as, the sawtooth signals which the signals 18 produce in co-operation with the integration network 9, 10'. The signals 17, 18 need not be accurately positioned relatively to one another since each type of signal co-operates with its own integration network 9, 10 and 9, 10' respectively. However, if, as denoted by the reference 20 in FIG. 5, a signal is missing because the particular needle concerned has broken oil, the associated capacitor 10' continues to be charged. The output voltage increases above the amplitude of the other sawtooth curves. Similar considerations apply in the case of a signal arriving too soon or too late. In the event of a too-soon signal, the distance between such signal and the next increases correspondingly, with the result that the associated capacitor experiences a voltage peak exceeding the normal sawtooth signal amplitude. Similar considerations apply in the event of a signal arriving too late; in such a case the interval between the immediately previous signal and the toolate signal is greater than normal and leads to sawtooth voltage peak.

The sawtooth signals are delivered, with decoupling provided by a diode 13, to the input of a threshold tripper 14. While the input thereto remains below the threshold or critical value, the tripper 14 outputs no signals. If irregular needle spacing or the absence of a needle produces a voltage peak across the capacitor 10 or 10', the voltage peak 21 (FIG. 5) in excess of the threshold value operates the device 14, which outputs a signal 22; the same is transmitted to a break relay 15 which interrupts the machine circuit 16.

FIG. 4 shows a few details of the evaluating circuitry shown in block schematic form in FIG. 3. The photoresistance 6 co-operates with a resistance R1 to form a voltage divider whose centre point is connected via a coupling capacitor C1 to the input of an amplifier 12 comprising a transistor T1 and resistances R2, R3, R4, R5. When the photo-resistance 6 is illuminated, the voltage at the centre point of such voltage divider alters, and the voltage variation is amplified by amplifier 12 and delivered via coupling resistance R6 to a threshold switch 38 comprising a transistor T2 and resistances R7, R8, R9. The threshold at which the transistor T2 operates is adjusted by means of the variable resistance R9. The switch 38 ensures that voltage variations occasioned by random reflections do not cause accidental triggering. Accordingly, the threshold is set so that only voltage variations produced by needle reflections are greater than the threshold value.

When the transistor T2 gates, a positive voltage step is produced at its output and goes, via a coupling resistance R10, an impedance converter comprising a transistor T3 and resistances R11, R12, and a coupling resistance R13 to the input of a transistor T4 co-operating with a resistance R14 and a diode D1 to form a discharge circuit for a capacitor C2 which corresponds to the integer 10 of FIG. 3. The charging circuit (constant-current source 9) for capacitor C2 extends by way of a transistor T5, a variable resistance R16 and a resistance R15. Through the agency of a Zener diode Z1, the biasing of transistor T5 is so adjusted that the same is conductive, so that the capacitor C2 is being charged continuously. When the transistor T4 gates, the discharge circuit for capacitor C2 is closed and the sawtooth curves 19, 20 of FIG. 5 are produced.

If a signal 17 or 18 (FIG. 5) is missing or arrives too soon or too late, the charge voltage of capacitor C2 increases. The steepness of the charging curve of the capacitor is determined by a variable resistance R16.

The potential across capacitor C2 is transmitted via a decoupling diode D5 to the threshold switch 14 comprising a transistor T6 and resistances R17, R18, R19, R20, R21. A variable resistance R20 is used to adjust the threshold of switch 14. When the voltage across capacitor C2 exceeds a predetermined value, transistor T6 gates. A negative voltage change is produced at the output of transistor T6 and goes, va a differentiating circuit comprising a capacitor C3 and a resistance R22, and a diode D2 to the base of a transistor T7. When a negative signal is applied to its base, transistor T7, whose emitter bias is adjusted by way of diode D3 and whose base bias is adjusted by way of a resistance R23, gates and energises a relay 15 in its load circuit. To delay its dropping, relay '15 is connected in parallel with a diode D4. Relay 15 stops the machine and, if required, initiates alarm signals.

The second electronic evaluating circuitry (not shown) is connected to the circuitry shown by way of the diode 13. When the machine is restarted, the electronic evaluating circuitry is reset to its initial state by means which are familiar to the skilled artisan and which are therefore not shown in detail.

The operation of the various electronic units, such as amplifiers, threshold switches and the constant-current source, is familiar to the skilled artisan and does not therefore need to be described in further detail.

I claim:

1. In a control apparatus for circular knitting :machines having knitting needles and for producing an indication when the yarn is not properly being knit by the machines, which apparatus includes a photoelectric sensing means for directing a light beam which is reflected back to a photoelectric receiver to produce electric signals indicative of the operational condition of the machine, the improvement comprising:

said sensing means being positioned so that the electrical signals are produced solely as a result of reflection from the needles, whereby said signals normally occur in a predetermined time sequence when said machine is in proper operating condition; and

detector means connected to said, sensing means for producing said indication when said signals vary from said predetermined time sequence. 2. In a control apparatus as set forth in claim 1, wherein said detector means includes:

an integrating network having an input, an output and a resetting connection;

means connected to said input of said integrating network for delivering a constant input signal to said network;

means connected to said sensing means and to said resetting connection of said integrating network to reset said integrating network as a result of the signals from the photoelectric receiver; and

tripping means connected to said output of said integrating network to produce said indication when the output of the integrating network exceeds a predetermined threshold.

3. In an apparatus as set forth in claim 2, wherein said integrating network includes a capacitor, said means connected to the input of the integrating network delivers a constant current to said capacitor, said means connected to said resetting connection efifecting a discharge of said capacitor upon the occurrence of each signal from the photoelectric receiver, whereby said capacitor produces a sawtooth series of output signals of a given amplitude at the output of the integrating network so long as said signals from the photoelectric receiver occur in said predetermined time sequence, said tripping means being responsive to the occurrence of an output signal in excess of said given amplitude.

4. In an apparatus as set forth in claim 3 for use with a knitting machine having two rows of needles, namely rib needles and dial needles, wherein said sensing means produces said electrical signals solely as a result of reflection from one row of needles, said apparatus including:

a second photoelectric sensing means positioned for producing electrical signals solely as a result of reflections from the other row of needles;

second detector means connected to said second sensing means and including:

a second integrating network having a second capacitor, means connected to said second capacitor for delivering a constant current to said second capacitor, and means connected to said second capacitor and to said second sensing means for discharging said capacitor upon the occurrence of the signals from the second sensing means; and

connecting means connecting the two capacitors to said tripping means, said connecting means including decoupling means comprising a diode.

5. In an apparatus as set forth in claim 4, wherein each of the means for discharging the respective capacitors includes an amplifier which applies a signal to the respective capacitor of the opposite Polarity from that of the current which charges the capacitor for thereby discharging the capacitor.

6. In an apparatus as set forth in claim 3, wherein the means for discharging the capacitor includes an amplifier which applies a signal to the capacitor of the opposite polarity from that of the current which charges the capacitor for thereby discharging the capacitor.

References Cited UNITED STATES PATENTS 8/1956 Van Alen et al. 66-157 OTHER REFERENCES MERVIN STEIN, Primary Examiner US. Cl. X.R. 

